Step 2: Changes to the Frame, Platen and Oven

Step 3: Test Run 2

I cleaned up and tested the oven and put everything together for another test. This time I had a fire extinguisher ready just in case. The plastic t...

This is the redesign of the vacuum forming machine I built this past summer. Here my first design Vacuum Former and if you look at the last step you can see why I redesigned it. If you don't know what a vacuum former is check out the links on the first step of my other instructable. I'm not going to go over everything again but you can use my other instructions to build the oven, platen, and frame. Only minor changes where made to these parts and a different base was made.

First I think I should go over why my old machine didn't work and why the new machine works a whole lot better. With my other design the plastic was heated while sitting above the oven, I did this because heat raises and I thought this would heat the plastic more effectively. As you see I underestimated how effectively this method actually heats the plastic. The plastic got to hot, sagged to much, touched the coils and caught on fire. The new design holds the plastic below the oven so that when it sags it falls away from the coils. It might not heat the plastic as fast but the heating process is much more controllable.

I can't quite figure out how you get the heated sheet in the frame from the oven to the platen. With the previous version it was straightforward - the frame was meant to flip-flop from one to the other. With this one - does it slide down the inner construction to the platen?

This is a really great design. I was wondering if I could use a couple of commercially available hot plates, bolted upside down into the upper box, instead of messing around with building my own heating elements?

Although not a complete success, you did show a lot of ingenuity with your heater box! Not only is your box insulated, the cement good heat retention to some degree as well. Thank you for taking the time to share it. Can you please post a video of Version 2? BTW, more holes will help on the vaccum bed. Also, you may see, sometimes vaccum formers draw the material with a male form, or air pressure, FIRST, before final form. That can help with 'webbing' on corners.

I started building a vauum former but I used perf board for the platten which has holes about every 1/2 in (I'm guessing, I'm not with the pice right now). I havent finished my oven yet but my guess would be if you had used the perf board (That stuff you hang tools on with hooks) you might be able to avoid the webbing since it has a vacuum source closer to every piece of the parts that you are duplicating, along with letting the plastic sag a bit more. This is just a theory at this point since my device isn't finished yet but it makes sense to me.

It would be great if you could annotate your photos a little bit. As far as the framing is concerned, have you considered grid beams? http://gridbeam.biz/photos.htm I have found them enormously useful in speeding prototype frames/structures.

I have landed a picture wall heater, which is basically the same as your upper section but comes pre made. My hope is to find one more of these and make a 30 x 60 inch vaccum former. This way I can only fire up half of it when I dont need the full size, or both when I do. Is there anything I should know electrically about these before I start hacking and cutting my wood stock pile up?

I don't have any experience with a wall heater, but it sounds like some thing I could use. Its basically a resistance heater like the coils I used right? It sounds like it would be well suited for a larger former.

As far as electrical stuff goes, I wouldn't touch it. Just mount it to your former and plug it in. I'd like to what you come up with some post an instructable or at least some pictures.

Its about 26 by 38 inches. I was planning to just remove the painted skin or face, to expose the inner coils. Im hoping to land two of them, so I can combine my CNC router projects with the vacuum former. I plan on making some custom car body parts.

Oven: I am making something similar but more compact. Oven is about 380 x 380mm and four Quartz heaters each 415W. Will use 20A diode to reduce heat if needed. Instead of concrete board I am using FIBEROCK. It is light, fireproof, quite solid and can be easily cut with utility knife. Board was $13CAN. I've tested board with butane torch. Eventually it would kind of burn but only at the edges and when torch was very close. Oven will have Al underlining and U-shaped reflectors to help distribute heat. I will also use thermostat since I've salvaged (new) B&D oven. It was under $50 and buying heaters on internet would cost more. Heaters have some kind of metal shields on top of them. They have some (smartly designed) holes that let heat more at the end of the heater than in the center. Comment: I think that vacuum table needs to have better surface than unfinished plywood. That would help creating better seal.

Good improvements from the original design. Part of you problem with the webbing comes from the sharp squared off angles of the pieces. The way around this to either make the sides shorter or lessen the angles. Or if thats not possible, use some gloves (heavy leather) and press down slightly at the corners prior to and slightly during the vacuuming stage. Don't press down too hard or you'll leave indentations or glove prints. The pressing also helps in certain spots that might be slightly recessed.

This may be a silly question, but what kind of plastic are you thermo forming? Where would it be typically available? Home Depot? On doing the thermo forming, I assume you wait till it has 'sagged' the appropriate amount, pull the holding frame toward you, then push it back against the back uprights as you drop it (place it gently that is) on the platten and your mold on the vacuum base. Is that about right? Great instructable. TIA

I used Polystyrene which you can get from many places except home depot or lowes. My first instructable has links to two companies on step six that you can get plastic sheet from. You can use other types of plastic but polystyrene is fairly common. And yes your description is exactly right.

For the webbing, get the plastic as hot as possible and possibly a bit of extra suction, that'll reduce the webbing distance a bit but there's always a limit to what the plastic can do, though if it doesn't hurt the design you could drop a mm or two of thickness and be careful bout heating and the webbing would be lessened, as would the overall strength of the design. By the way I did and interesting experiment in making a tube on the vacuum former and found that with thick plastic you do some interesting stuff by stretching it with the vaccuum. It picks up way more detail.